Sometimes they are unavoidable in cities where the space between buildings isn't wide enough to accommodate two lanes, bit generally I find them highly inconvenient. In my city, you always have to look both ways REGARDLESS because it is common to see cars approaching you from the wrong direction. Once, when apartment hunting a few years ago, my soon-to-be roommate inadvertently turned the wrong way onto a one-way street at night, when the area was poorly lit. He noticed his mistake quickly and since there was no traffic he chose just to back up and turn around.... then we noticed we were right in front of the local police station. Luckily they didn't notice us!